Disclosed herein are portable teleconferencing products that implement a doubletalk detector in a low frequency range or in a frequency range commensurate with the frequencies through which sound may be efficiently transferred between a speaker and a microphone through an enclosure. Also disclosed herein are teleconferencing systems that implement a secondary doubletalk detector, a non-presumptive doubletalk detector, a confirmatory doubletalk detector, and/or a false doubletalk detector, whereby echo cancellation coefficients may be better adapted after echo path changing events through the use of accelerated coefficient adaptation or half-duplex operation until adaptation is restored. Further disclosed herein are teleconferencing products that include more than one port for communicating with distant parties or a single party and a local source of audio material, whereby one distant party is prevented from being transmitted to it private audio from another party or another audio signal while permitting a local participant to hear the private audio. Detailed information on various example embodiments of the inventions are provided in the Detailed Description below, and the inventions are defined by the appended claims.
The reader is referred to the following U.S. Patents for background information. U.S. Pat. No. 5,933,495 to Oh describes a subband acoustic echo canceller that includes the freezing of filter coefficients on detection of near side speech. U.S. Pat. No. 5,937,060, also to Oh, describes a residual echo suppression system in connection with an echo canceller. U.S. Pat. No. 6,990,194 to Mikesell et al. describes the use of sub-banded voice activity detectors coupled to an echo cancelling circuit. All of these references are hereby incorporated by reference as background material for the description that proceeds below.
The claimed systems and methods relate generally to loudspeaker teleconferencing systems that utilize echo cancellation and full duplex operation with distant participants, and more particularly to teleconferencing systems that implement narrow-band doubletalk detectors, secondary modes of doubletalk detection and partial mixing of audio between two far side participants or one far side participant and a local audio source.